Hi Samha, this is a question of the size of the particles. Finely dispersed magnetic nanoparticles adhere to a carbon-coated grid. A magnetic FIB lamella is also no problem in the TEM. The thinned specimen must be screwed tightly into the specimen holder If the volume fraction of magnetic particles is large, however.

When working with magnetic samples in TEM you must correct the rotation center and the astigmatism of the objective lens then ever.

In our lab we also do HRTEM with magnetic specimen. It works!

There are demagnetizing tools available which reduce the magnetization dramatically. There are even labs which do not allow to investigate magnetic particle in their TEM since if they "disappear" within the column or attracted by the magnetic lenses the quality of your TEM becomes less controllable. 

the tem , sem and the hrtem are an importants tool to see the effect of The magnetic field in the arrangement of the magnetic meso particule in the sample

in addition , the size particule variation as function of the magnetic field

Dear Samha,

I only add some comment on Armand Béché's answer.

There are three types of FE-SEM: 1. with immersion lens (B all ober the chamber), 2. semi-immersion (B only close to the polepiece) and 3. classical, no-immersion.

You must seak for the third type - without any immersion. The spatial resolution is little bit limited, but hopefully not that much for you as you want to see the microstructures.

For example TESCAN's MIRA microscope (no immersion) has the resolution below 2 nm.